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<head>
  <meta charset="UTF-8">
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  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <input id="text" type="text">
  <button id="btn">click</button>
  <script>
    const btn = document.getElementById('btn')
    const text = document.getElementById('text')
    btn.onmousedown = function (e) {
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    }
    btn.onmouseup = function (e) {
      text.blur()
    }
  </script>
</body>

</html>